Blood purification systems, which are used for conducting hemodialysis, hemodiafiltration or hemofiltration, involve the extracorporeal circulation of blood through an exchanger having a semi permeable membrane. Such systems further include a hydraulic system for circulating blood and a hydraulic system for circulating replacement fluid or dialysate comprising blood electrolytes in concentrations close to those of the blood of a healthy subject. Most of the conventionally available blood purification systems are, however, quite bulky in size and difficult to operate. Further, the design of these systems makes them unwieldy and not conducive to the use and installation of disposable components.
Standard dialysis treatment, using an installed apparatus in hospitals, comprises two phases, namely, (a) dialysis, in which toxic substances and scoriae (normally small molecules) pass through the semi-permeable membrane from the blood to the dialysis liquid, and (b) ultrafiltration, in which a pressure difference between the blood circuit and the dialysate circuit, more precisely a reduced pressure in the latter circuit, causes the blood content of water to be reduced by a predetermined amount.
Dialysis procedures using standard equipment tend to be cumbersome as well as costly, besides requiring the patient to be bound to a dialysis center for long durations. While portable dialysis systems have been developed, conventional portable dialysis systems suffer from certain disadvantages. First, they are not sufficiently modular, thereby preventing the easy setup, movement, shipping, and maintenance of the systems. Second, the systems are not simplified enough for reliable, accurate use by a patient. The systems' interfaces and methods of using disposable components are subject to misuse and/or errors in usage by patients. For a portable dialysis system to be truly effective, it should be easily and readily used by individuals who are not health-care professionals, with disposable input and data input sufficiently constrained to prevent inaccurate use.
There is also a need for a portable system that can effectively provide the functionality of a dialysis system in a safe, cost-effective, and reliable manner. In particular, there is a need for a compact dialysis fluid reservoir system that can satisfy the fluid delivery requirements of a dialysis procedure while integrating therein various other critical functions, such as fluid heating, fluid measurement and monitoring, leak detection, and disconnection detection. The reservoir system must be weighed consistently and accurately to insure that the amount of water in the reservoir is always known and so volumetric controls can be applied based on the calculated water levels. In addition, since the reservoir system is subject to insertion into and removal from the dialysis machine by the user, it must be configured to minimize the possibility that variance in weight measurement will be generated by an improper positioning of the reservoir pan or leakage of water onto the weight measurement system. Therefore, a need exists for a weight measurement system that can effectively measure the liquid level in a reservoir system.
To address these needs, U.S. patent application Ser. No. 13/023,490, which is entitled “Portable Dialysis Machine”, filed on Feb. 8, 2011, assigned to the applicant of the present application, and herein incorporated by reference in its entirety, describes a “dialysis machine comprising: a controller unit wherein said controller unit comprises: a door having an interior face; a housing with a panel wherein said housing and panel define a recessed region configured to receive said interior face of said door; and a manifold receiver fixedly attached to said panel; a base unit wherein said base unit comprises: a planar surface for receiving a container of fluid; a scale integrated with said planar surface; a heater in thermal communication with said planar surface; and, a sodium sensor in electromagnetic communication with said planar surface.”
The dialysis machine includes a reservoir unit for storing non-sterile water. Upon initiation of the dialysis machine, the water passes through a sorbent filtration process, then through a dialysis process, and finally back into the reservoir. The dialysis machine also includes a flexure system for flexibly receiving and suspending the reservoir pan and for measuring the water weight. The flexure system comprises a series of four flexures, each positioned at a corner of a rectangular shaped reservoir pan and each integrated with a Hall sensor. It has been found that the four cornered flexure system has certain functionalities that can be improved upon. Particularly, use of the four cornered flexure system may lead to weighing inaccuracies arising from oscillation of the system and creep arising from the averaging operation of data over the four flexure units. Therefore, what is needed is an improved reservoir unit weight measurement system configured to reduce weighing inaccuracies.